Thyristor operated photosensitive control for lamp bank display

ABSTRACT

This disclosure is concerned with a mechanical display selector and electronic control mechanism for a lamp bank comprising a series of rows of lamp units arranged geometrically to produce any desired lighted message thereon. The individual lamps are controlled by solid state components in an auxiliary control circuit which operates at power requirements much below those of the lamp bank itself. The control circuitry is completely isolated from the lamp bank power supply. The selection of lighted lamps is attained mechanically by apertured cards interposed between a light source and photocell units which are in series with the gate connections of thyristor devices or gate controlled semiconductors interposed in the lamp unit circuits. In addition, the indexing cards, the actuation of the read lamps, the activation of the photocells and the application of holding current to the thyristor devices or pulse controlled conductors are all sequentially controlled to provide a cycle of operation in which the selected display on a card is indexed, read, and displayed by lighted lamp units. The entire cycle of operation is automatic and the chosen cycle of displays is repeated until the unit is turned off.

United States Patent 83814 [21] Appl.No. 635,223 221 Filed May 1,1967

[45] Patented Jan. 12, 1971 [54] THYRISTOR OPERATED PHOTOSENSITIVE CONTROL FOR LAMP BANK DISPLAY INDfX WI/fft CONTROL POWER 50 sou/:05

OTHER REFERENCES SCR Manual" General Electric 1964 Primary Examiner-William F. Lindquist Assistant ExaminerC. M. Leedom Attorney-Keith S. Bergman ABSTRACT: This disclosure is concerned with a mechanical display selector and electronic control mechanism for a lamp bank comprising a series of rows of lamp units arranged geometrically to produce any desired lighted message thereon. The individual lamps are controlled by solid state components in an auxiliary control circuit which operates at power requirements much below those of the lamp bank itselfv The control circuitry is completely isolated from the lamp bank power supply. The selection of lighted lamps is attained mechanically by apertured cards interposed between a light source and photocell units which are in series with the gate connections of thyristor devices or gate controlled semiconductors interposed in the lamp unit circuits. In addition, the indexing cards, the actuation of the read lamps, the activation of the photocells and the application of holding current to the thyristor devices or pulse controlled conductors are all sequentially controlled to provide a cycle of operation in which the selected display on a card is indexed, read, and displayed by lighted lamp units. The entire cycle of operation is automatic and the chosen cycle of displays is repeated until the unit is turned off.

LAMP BAN/4 Pam PATENTEU m 219?:

sum 2 or 5 INVENTOR. RICHARD M. Sue-Rum ATTYS.

SUMMARY OF THE INVENTION AND OBJECTS THEREOF The novel contribution of this disclosure resides in the control circuitry being electrically isolated from the power circuitry required to operate the rather high electrical load of a lamp bank. By using a low power circuit to control the lamp banks, one can more effectually ensure proper control circuitry operation within practical limits. In addition, there is provided a mechanical card positioning device for varying the selected display in a chosen sequence, this device being most simple in operation and easily mastered by one responsible for changing the chosen messages.

It is a first object of the invention to provide a practical sign control for lamp banks wherein the control itself is operated at a low power level.

Another object of the invention is to provide a lamp bank control using solid state components where, possible to eliminate the inherent difficulties of switches and relays.

Another object of the invention is to provide a versatile lamp bank control easily modified to meet size and display requirements of any physical application. The capacity of the control is highly flexible and can range from lamp banks having only a few rows of lamp units to lamp banks of 100 rows or more.

These and further objects will be evident from the following detailed disclosure of a preferred embodiment of the invention, taken together with the accompanying drawings. This embodiment is only presented by way of example and is not to limit the scope of the invention disclosed herein. In the DESCRIPTION OF THE PREFERRED EMBODIMENT The following disclosure is concerned with a lamp bank controlling device wherein almost all of the control functions for individual lamps are controlled by solid state electronic circuits using available pulse controlled conducting devices. This has the advantage of eliminating common problems posed by the use of mechanical switches and contacts to handle lamp bank loads. Furthermore, the circuitry described herein isolates the low voltage and current control circuitry from the heavier main power supply used to light the lamps. In this manner, a more easily controllable low voltage circuit can be used to-operate the sometimes great electrical loads imposed by a large lamp bank of several hundred lamps.

The control circuitry disclosed herein utilizes various combinations of pulse completed circuits designed about thyristor devices presently available in practical sizes for this purpose. Thyristor devices embrace a family of solid state elements generally describable as pulse controlled semiconductors. Such devices include a controlling gate or pulse terminal where a firing current is applied to a gate or is superimposed in the conducting anode-cathode connections to cause the device to conduct current. The two specific devices used in this disclosure are silicon controlled rectifiers (SCR)-each having a gate connection, cathode terminal and anode terminal; the triacs-each having a gate connection and two anode terminals. Other similar thyristor devices might be used in place of the specific examples given herein. These devices are described generically by reference to a pulse connection, which might be one or more gate terminals or a circuit superimposed on the controlled circuit and by reference to anode-cathode terminals, which might be two anode terminals, two cathode terminals or any combination of the two through which the controlled circuit is conducted.

GENERAL DESCRIPTION The basic apparatus is illustrated schematically in FIG. I. It includes a mechanical control drum at which the geometric pattern of lighted lamps is preselected on changeable cards. This drum is generally designated by the numeral 10. The cards 11 are apertured in a preselected pattern so as to pass light from a stationary light source, shown as a row of read lamps 12 within drum 10. Light from lamps 12 is applied to an exterior pattern of photocells mounted in an assembly designated generally by the numeral 13. The geometric pattern and number of the light receptive members in the individual photocells in the assembly 13 corresponds geometrically and numerically to the arrangement of lamp units 14 in the lamp bank 15. As used herein, a lamp unit might be a single lamp or a cluster of lamps, depending upon the particular type of display.

Each lamp unit 14 is controlled by a gate controlled semiconductor, shown as an individual lamp power thyristor 16, specifically an SCR, the gate connection 17 for each SCR being respectively wired to the photocell in assembly 13 corresponding to the lamp unit 14 controlled thereby.

A primary power source 18 is provided for the lamp bank 15, the power source 18 being used to provide a full wave DC signal across said lamp units 14. This cyclical signal will vary from maximum voltage to zero. The anode-cathode terminals of each thyristor 16 are wired in series with an individual lamp unit 14 across the main power source 18.

Isolated from the power supply 18 is a control unit 20 having an independent connection to a power source. The control unit 20 serves to control operation of thyristors 16, the photocells at 13, lamps l2 and the motor 21 that indexes the drum l0. Rotational motion of drum 10 is monitored by an indexing wheel 22 which turns in unison with drum 10. Wheel 22 has an angularly recessed periphery which operates an indexing switch 23 and a mechanical linkage 24. The linkage 24 physically moves the photocell assembly 13 apart from drum 10 while drum 10 is being rotated. (See FIGS. 3, 5).

The individual thyristors l6 require a positive current on the gate leads 17 before they will conduct current to complete the lamp circuits through their individual anode-cathode terminals across the power supply 18. This firing current is selectively provided during operation of the control unit 20, through the light-actuated photocells in assembly 13. The lamp 12 and drum l0 cooperate to provide a controllable light source at the photocells to produce the desired lighted pattern on lamp bank 13. Each SCR 16 is normally maintained in an off condition by a small negative voltage applied to its gate terminal 17 in order to ensure that it remains off when it is not to conduct. This small negative bias is provided by the forward voltage drop of two diodes 25 in series with the lamp power supply. When all of the lamp units 14 are turned off by the thyristors 16, the negative bias is provided by a negative conductor 26 from the control unit 20.

In this apparatus, the thyristors 16 are fired by momentary lighting of the read lamps 12 to activate, through the apertured card or drum 10, the selected photocells in assembly 13. The reception of light at the photocells varies the resistance thereof and applies a positive voltage to the selected gate terminals 17. This causes the selected thyristors 16 to tire and completes a power circuit to the chosen lamp units 14 required for a particular display. The continuance of the dis play is provided by a low voltage filtered DC signal applied across the anode-cathode terminals of thyristors 16 across lines 26 and 27 from the control unit 26. This memory or holding current prevents the voltage across the anode-cathode circuit of each conducting thyristor 16 from falling to zero. This holding voltage maintains the tired thyristors 16 in a conducting state until the current is removed. While the thyristors in are maintained in this conductive state, the read lamps 12 can be cooled and the cards 11 can be mechanically shifted by rotation of drum to prepare the apparatus for the next display as controlled by the apertures on each card 1 ll.

ELECTRONIC CONTROLS The control circuitry is shown in detail in MG. 2. As illustrated, one section of the lamp bank power connections is detailed, there being provision made for two additional sections identical to that shown. Using available components, a single section can readily handle a lamp bank load up to 50 amps. If the total lamp bank load is greater, a second section can be used for a load up to 100 amps, and a third section for a load up to 150 amps. The sections can be provided with power from separate phases of a power supply or from completely independent power sources. If a greater lamp bank load is required, additional sections can be provided or larger power supplies utilized.

The lamps units 14 are Wired in groups independently fused at 28 to a positive bus 32 of the main lamp bank power supply 18, shown as a transformer 30 with a filter circuit 31 to provide a full wave direct current signal. The negative bus 33 is connected across the gate terminal 17 of each SCR 16 through limiting resistors 34. As described above, two biasing diodes 25 are also wired in series with the main lamp power supply across the lines 32, 33. Each section of the lamp power circuit also includes a cathode bus 35 and positive terminal connection 36 for the memory circuitry, as well as a read bus 37 and negative terminal connection 38 for control of the individual photocells. 40. Each photocell 40, positioned as described above in the assembly 13, is wired across the read bus 37 in series with the gate terminal 17 of the SCR in controlled thereby.

The read bus 37 is supplied with an interruptible DC gate signal from a transformer 41 through a line 42 connected to a read bus 37 and a line 43 connected to a negative terminal connection 38. The primary winding 44 of the read driver transformer 41 is wired in series with a thyristor device (triac) 45 across lines 46 and 47 powered by a winding 48 on a main memory circuit power transformer 50. When triac 45 is in a conducting state, a low voltage positive signal will be provided at lines 42 and 43 to fire the thyristors 16 having gate connections 17 wired in series with conducting photocells 40. The photocells are of the resistance type and constitute variable conductive means wherein the electrical resistance of each photocell 40 will be reduced when light is received thereon from the read lamps 12. When not activated, photocells 4t) block application of the firing current to the thyristors 16.

The low voltage direct current signal applied to the cathode bus 35 and the positive terminal connection 36 is provided from a winding 51 in the transformer 59 through a filtering circuit generally shown at 52, there being a thyristor (SCR) 53 interposed in series with the output connections at lines 54 and 55. The thyristor 53 is driven by a pulse applied from a transformer winding 56 supplied by a primary winding 57 also powered across lines 46, 47 in series with a triac 58. The output winding 56 is applied through a rectifying bridge 6'1) and directed to line 55 and the gate terminal 59 of the thyristor 53. The purpose of thyristor 53 and the driving circuit controlled by winding 56 is to permit interruption of the constant low voltage signal applied across the cathode-anode circuit of the thyristors 16. This signal provides a memory" or holding current to maintain each thyristor 16 in operating or conducting condition after being initially fired by reception of the necessary gate signal. The thyristor controls are therefore embodied in the low voltage circuitry supplied by windings 511 and 56, which are more easily controlled than the more powerful currents that would have to be interrupted in order to control the lamp unit 14 directly from the main power supply.

The control circuitry is supplied with electrical power from an AC power source at terminals denoted by the numeral til.

A main power switch 62 is provided, by which the entire apparatus can be activated or deactivated. A pilot lamp 63 is utilized to indicate that the switch 62 is closed. Power is applied from terminals bl through a common line 64 and a line 65, both of which are directly connected to the primary winding of the main power transformer 50.

The indexing motor 21 is controllcd by a relay 66 having a set of normally open contacts connected between one motor lead 67 and the gate connection of a triac 63. The conductor 67 is wired to one side of the triac its remaining side being connected to the common conductor 64 T he contacts of relay as, when closed, cause the triac as to conduct and complete a power circuit to the motor 21, whose remaining terminals are connected directly to line 65. Wired in parallel with the contacts of relay as is the normally open index switch 23, which is controlled by the mechanical index wheel 22 (FIG. 1). Switch 23 maintains the motor 21 in operating condition until the drum 10 has been indexed to its next position.

The read lamps 12 are controlled by a second relay 70 also having normally open contacts which control the gate signal to a similar triac 71. The anode terminals of triac 71 are connected respectively to a line 72 wired to the lamps and to the common line 64. The remaining side of each lamp 12 is wired to the line 65 to complete the lamp circuit. The read lamps 12 will be lighted when the relay 70 has been activated to close the contacts thereof.

The sequence of operation of the various components described above is controlled by a solid state stepping circuit generally shown in the upper portion of FIG. 2A. Thestepping circuit is provided with direct current power at a low voltage from a winding 73 of the transformer 50 and a filter circuit generally shown at 74. The resulting DC current is applied to a positive bus 75 and to a negative bias conductor 76. The positive bus 75 is wired in series with a two position run-stop switch 77 wired in series with a variable resistor 78 that controls the length of display time of the lighted lamp units 14. When switch '77 is in its stop position, the mechanism does not step, but remains operable with the last selected display shown on the lamp bank 115. In the run position, the mechanism will continue to step from message to message at a rate determined by the setting of the variable control provided by the resistance 75;. The resistance 78 is wired in a pulse circuit generally designated by numeral 8t). This circuit includes a transistor til and provides a timed pulse at the key 82 for the four-stage stepping circuit composed of multivibrator circuits. The stepping circuit sequentially provides a pulse at four outlets designated respectively by the reference numerals 83, 84, 85 and 86. The pulse duration at the outputs 83 to 86 determines the timed sequence of operation of the mechanisms previously disclosed.

The pulse from output 83 is directed through a line 87 to the relay as, and is operable to close the contacts of relay 66 and begin operation of the indexing motor 211. The pulse also is directed through a line 83 to the gate of triac 58, and serves to continue conduction of triac 58, thereby driving the already operating memory circuitry.

The pulse from output M is directed through line 90 to the coil of relay 70 and is operable to close the contact thereof and complete a circuit to thread lamps 12. This pulse is also directed through line 91 to avariable resistance providing control of the time in which the lamp units of lamp bank 15 are unlighted, or off time control, this resistance being designated by numeral92. Resistance 92 is wired in parallel with the previously described resistance 78 and serves to shorten the length of the pulse produced by the circuit 8f) when the signal is applied therethrough.

The pulse produced at output 85 is directed through line 93 to the gate of triac 4-5, activating the circuitry that controls the photocells 40. it also is directed through line 34 to the line 8% to drive the memory circuit. Further, it is directed through a line '95 to the line 9th to maintain the read lamps T2 in operation. The pulse is fed through a constant resistance 96 back into the pulse circuit iii), resistance 96 being in parallel with the display time-controlling resistance 78.

The pulse at output 86 is directed through line 94 to line 88 to maintain the driver transformer coil 57'of the memory circuit in operation. It is returned to the pulse circuit 80 through a fixed resistance 97 to control the cooling time for read lamps l2.

A contactor is provided in the lamp power supply for varying lamp brightness. As shown, this comprises double pole contacts 115 connected to selected taps of the transformer 30. The relay coil 116 that controls operation of contacts 115 is preferably operated by a photocell relay 117 connected directly to the control circuit power line 64, 65.

The operation of the relay coil 116 varies the voltage applied to the lamp'units 14 for day and night operation. The relay coil 116 might also be controlled by a programmed motor operated relay to change the power to lamp units 14 in a timed cycle.

MECHANICAL LIGHT CONTROLS The mechanical details of the drum apparatus are shown in greater detail by FIGS. 3 through 5. Basically, the drum comprises two circular end plates'100 journaled by collars 101 fixed to them and rotatably carried by a fixed central shaft102 on the frame of the apparatus. The shaft 102 serves to support the base 103 for the read lamps 12, as well as providing rotational support of drum 10. The drum 10 includes a cylindrical transparent wall structure 104 having longitudinal frames 105 for reception of message cards from the left-hand end as viewed in FIG. 3. The drum 10 isrotated by a synchronous motor 21 (low speed) through a belt and pulley drive generally shown at 106.

The message cards 11 are simply rectangular strips of opaque paper on which are printed 21 series of circles corresponding in position to the positions of the individual photocells 40 in the assembly 13 (FIG. 4) The assembly 13 mounts a group of photocells in a solid block with the light receptive elements thereof open toward the drum 10. The cards 11 are punched or otherwise. opened to permit the passage of light toward each photocell 40 which is to be activated during display of a chosen method. The cards 11 and assembly 13 are positioned such that the reading of a message on each card 11 will be direct, so that one programming the card 11 must merely punch holes in the 'cardcorresponding to the message, word'or symbol which he wishes to be displayed on the lamp bank 15.

The assembly 13 must be mounted'directly to the card 11 being read thereby. lts upper face is curved along its length complementary to the exterior curvature of the mounted cards 11. The assembly 13 is carried by arms 107 fixed thereto and pivoted to the apparatus frame at'108 about an axis parallel to the drum axis.

At the right-hand end of drum 10 (FIGS. 3 and 5) is the index wheel 22, which is fixed to the collar 101, and thereby rotates in unison with drum 10. Wheel 22 is provided with indentations 110 about its periphery, each indentation 110 being angularly aligned with the respective longitudinal porrions of the card frames 105. A cam 'follower 111 rides along the peripheral edge of wheel 22 and is of a size such that it can fit inwardly into the individual indentations 110. It is carried by a short lever 112 fixed to the adjacent lever 107, and thereby serves to angularly position the assembly 13 about the pivots 108.

When the cam follower 11 is fitted within an indentation 110, the assembly 13 will rest directly'against the card 11 being read thereby, being biased upwardly by a small spring 113. During rotational movement of the'drum 10 and index wheel 22 the cam follower 111 will hold the assembly 13 at a position slightly outward from the drum so as to provide clearance for drum rotation as shown in dashed lines in FIG. 5. The same cam follower 111 is used to close the normally open index switch 23 so that the switch 23 is closed during movement of the wheel 22 from one angular position to the next. It is the switch 23 that maintains the motor 21 in operating condition once rotation of the drum 10' is initiated and until the next angular position of drum 10 have been attained.

OPERATION The operation of the apparatus is believed to be generally understood from the above description. The mechanism can be used to handle any size of lamp bank 15. The program cards 11 may be printed to control any length of lamp bank. Only as many as are actually in use will punched to select a message. The drum 10 as shown holds six program cards, although obviously more can be provided for by enlarging its size. The rotational movement of the drum changes the message on the lamps bank and continues in a repetitive fashion. during normal operation. To change a card 11, the apparatus may be rendered inoperative by opening power switch 62 or the stop-run switch 77 may be opened, which will maintain the last display on the lamp bank 15. When the run-stop switch 77 is open, the stepping circuitry will continue thecycle previously initiated but will not step to the next indexing cycle until the switch 77 is again closed. When the run-stop switch 77 is open, and the power switch 62 is closed, the drum 10 can be manuallyrotated by depressing the photocell assembly 13 until switch 23 causes the motor to rotate. The assembly 13 can then be released and the drum 10 will index to the next card position and stop. This will not affect the message displayed on the lamp bank'lS, where the last cycled message will remain lighted. r

The power switch 62 controls only the power to the electronic control equipment and does not affect the main power to lamp bank 15 or to the thyristors 16. The control power circuits are completely isolated from the more heavy lamp circuits. However, when the control power switch 62 is open, the

lamp bank 15 will be turned off, since no control pulses will be applied to the thyristors 16 to maintain the lamp units 14 in a lighted condition.

The operation of the mechanism can be viewed as a fourstage cycle which will continually be repeated with a different message being displayed during each cycle. During the first stage of the cycle, when the stepping circuit output pulse is provided at output 83, the lamp bank display is lighted on a preselected message held by operation of the memory circuit components, which superimpose alow voltage direct current signal through the thyristors 16, acting as a holding current after release of the firing pulse applied at the desired gates 17. During this first stage, the read lamps 12 are unlighted and the photocells 40 are inactive, since no-signal is applied to the triac 45 that controls transformer winding 44. During the first stage, a pulse is provided to the relay 66 that controls index motor 21, and the drum 10 will be indexed to its next angular position, controlled by the mechanical elements described above. The drum 10 will be in position for application of the next message to the mechanism prior to completion of the lighted display duration at lamp bank 15.

During stage two of the cycle, the lamp bank 15 is unlighted. The memory circuit current is removed from thyristors 16 by removal of the pulse from the triac 58 and windings 57 of the driving transformer. All of the lamp units then are deactivated. The read lamps 12 are lighted by application of a pulse to the coil of relay and quickly warm up to their fully lighted level. The photocells 40 are still inactive since no pulse is directed to triac 45. The motor 21 will remain stationary at all times except during the initial portion of the first stage of the cycle.

During the third stage, when the pulse is produced in the stepping circuit at output 85, the memory circuit, the read lamps and the photocells are all active. The output pulse at this stage is directed to triac 58 and triac 45 to drive the memory circuit power supply and to provide a gate signal through the thyristors 16 through the selected photocells 40 whose resistance is lessened by reception of light thereby. This will light the lamp units 14 in the lamp bank 15 corresponding to the message chosen by the holes in the message card 11 adjacent to the photocell assembly 13.

The fourth stage operation, when the pulse is directed through output 86 of the stepping circuit, holds the memory circuit on by application of the signal to triac 58. The read lamps 12 are permitted to cool during this time and the photocells 40 are inactive. The previously selected thyristors 16 will remain in a conducting stage since the holding current provided by the memory circuit will continue uninterrupted through this stage as well as through the subsequent first or indexing stage just described.

This apparatus provides a practical and simple manner of controlling a variable message on a lamp bank. It permits the use of lamp banks having much greater power requirements than could bedirectly controlled by use of control circuits in series with the lamp terminals. In addition, the card message change is easily mastered by one having no electronics background and can be readily programmed for any desired type of message display. The use of solid state components as described provides a control mechanism that minimizes malfunctions, particularly since the control circuits are generally at low power applications in relation to the power requirements of the lamp bank itself.

While the above description discloses in detail the preferred form of the apparatus it is to be understood that the details of the structure are not intended to limit the scope of the invention itself except as set out in the following claims.

lclaim: 7

1. in an apparatus for controlling the illumination of a plurality of independent lamp units arranged geometrically in alamp bank and supplied with primary lamp power from a source of electrical energy wherein the electrical current cyclically reaches zero:

individual lamp power thyristor means each having a pulse receiving connection and anode-cathode terminals, the anodecathode terminals being respectively connected in a series circuit with the individual lamp units to selectively complete a power circuit therethrough from said source of electrical energy across the respective individual lamp units following reception of a firing pulse at the pulse receiving connection of the lamp power thyristor connected thereto and to continue to conduct current across the anode-cathode terminals during recep tion of holding current thereby;

a firing current source;

first control thyristor means;

variable conductive means in a series circuit with the pulse receiving connection of each of said lamp power thyristor means and the anode-cathode terminals of said first control thyristor means across the firing current source, said variable conductive means being selectively conditioned to blockthe reception of firing current at the individual pulse receiving connections or to permit application of firing current at said pulse receiving connections;

a holding current source producing a constant current output; and

second thyristor means operatively connected in series with the anode-cathode terminals of said lamp power thyristor means across said holding current source.

2. An apparatus as defined in claim wherein'said variable" conductive means comprises individual photocells each having a variable resistance resistance element in series'with the pulse receiving connection of the lamp power thyristor means controlled thereby.

3. An apparatus as defined in claim 1 wherein said variable conductive means comprises:

individual photocells each having a variable resistance element in series with the pulse receiving connection of the lamp power thyristor means controlled thereby; and controllable light means directed to said photocells to vary the electrical resistance of preselected resistance elements thereof. 4. An apparatus as defined in claim 3 further comprising: sequentially operable control means connected to said control light means and to said first and second control thyristor means to: a. control the application of light from said controllable light means to the photocells; and

b. actuate said first andlsecond, control thyristor meansb,

application of a firing pulse to the pulse receiving connec-' tions thereo and p I v c. and to maintain the actuation of. said second control thyristor means following deactivation of said controllable light source and said first control thyristor means.

6. in an apparatus for controlling the illumination of a plurality of independent lamp units arranged geometrically in a lamp bank:

light responsive conduction means, including a plurality of light receptive members each corresponding to one of the lamp units and arranged in a pattern geometrically corresponding to the arrangement of the respective lamp unitsin the lamp bank;

read lamp means directed toward the light receptive mem- ,bers of said light responsive conduction means; I read lamp power supply means; read lamp control means interposed in series with said read lamp means in a circuit. across saidgread lamp power supply means to selectively complete a powercircuit to saidread lamp means;

light controlling means physically interposed between said light responsiveconductionmeans and said read lamp means to selectively pass a lightpattern therethrough into preselected light receptive members in a pattern geomet rically corresponding to the desired lighting pattern o f the lamp units in the lampbank; T

lamp unit power supply meansv to provide a pulsating lighting current forsaid lamp uni,ts;- gate controlled rectifier means l laying independent cathode-anode circuits interposed; in {series with each lamp unit across said lamp unit power supply means; gate power supply means producing an"intermittentgate signal having a peak voltage and current adequate to fire said gate controlled rectifier means;

each light receptive element being interposed in a series cire;

cuit between the gate power supply means and each gate connection of said gate controlled rectifier 'meansconnected with the lamp unit corresponding thereto;

a memory circuit power supply operable, when activated; to produce a filtered holding current at the output thereof: and

memory circuit control rheans to selectively actuate said memory circuit power supply, the output of said memoryv circuit power supply being applied to a cathode-anode connection common to said gate controlled rectifier means. i

7. An apparatus as defined in claim 6 wherein said light controlling means comprises:

an axial drum having longitudinal message cards mounted thereon;

each of said message cards being provided with preselected apertures to pass light to selected light receptive members of said light responsive conduction means; and

said light receptive members being longitudinally aligned adjacent to said drum in a position facing one of said message cards.

8. An apparatus as defined in claim 7 wherein said read lamp means is mounted in a stationary position inside said drum and light therefrom is directed toward the light receptive members through one of said cards.

9. An apparatus as defined in claim 7 further comprising: an intermittently operable motor mechanically connected to said drum to selectively shift said drum to bring a preselected card ight from saidgontiaulibie mounted thereon into a position interposed between said read lamp means to said light receptive members; and lamp means and said light receptive members. 1 indexing means operatively connected to said light con- 10. An apparatus as defined in claim 6 wherein said light trolling means to position a selected one of said cards controlling means comprises: .1 between said read lamp means and said light receptive a plurality of cards each being apertured to provide a memberspreselected light pattern therethrough from said read 

1. In an apparatus for controlling the illumination of a plurality of independent lamp units arranged geometrically in a lamp bank and supplied with primary lamp power from a source of electrical energy wherein the electrical current cyclically reaches zero: individual lamp power thyristor means each having a pulse receiving connection and anode-cathode terminals, the anodecathode terminals being respectively connected in a series circuit with the individual lamp units to selectively complete a power circuit therethrough from said source of electrical energy across the respective individual lamp units following reception of a firing pulse at the pulse receiving connection of the lamp power thyristor connected thereto and to continue to conduct current across the anode-cathode terminals during reception of holding current thereby; a firing current source; first control thyristor means; variable conductive means in a series circuit with the pulse receiving connection of each of said lamp power thyristor means and the anode-cathode terminals of said first control thyristor means across the firing current source, said variable conductive means being selectively conditioned to block the reception of firing current at the individual pulse receiving connections or to permit application of firing current at said pulse receiving connections; a holding current source producing a constant current output; and second thyristor means operatively connected in series with the anode-cathode terminals of said lamp power thyristor means across said holding current source.
 2. An apparatus as defined in claim wherein said variable conductive means comprises individual photocells each having a variable resistance resistance element in series with the pulse receiving connection of the lamp power thyristor means controlled thereby.
 3. An apparatus as defined in claim 1 wherein said variable conductive means comprises: individual photocells each having a variable resistance element in series with the pulse receiving connection of the lamp power thyristor means controlled thereby; and controllable light means directed to said photocells to vary the electrical resistance of preselected resistance elements thereof.
 4. An apparatus as defined in claim 3 further comprising: sequentially operable control means connected to said control light means and to said first and second control thyristor means to: a. control the application of light from said controllable light means to the photocells; and b. actuate said first and second control thyristor means by application of a firing pulse to the pulse receiving connections thereof.
 5. An apparatus as defined in claim 3 further comprising: sequentially operable control means connected to said control light means and to said first and second control thyristor means to: a. control the application of light from said controllable light means to the photocells; b. actuate said first and second control thyristor means by application of a firing pulse to the pulse receiving connections thereof; and c. and to maintain the actuation of said second control thyristor means following deactivation of said controllable light source and said first control thyristor means.
 6. In an apparatus for controlling the illumination of a plurality of independent lamp units arranged geometrically in a lamp bank: light responsive conduction means, including a plurality of light receptive members each corresponding to one of the lamp units and arranged in a pattern geometrically corresponding to the arrangement of the respective lamp units in the lamp bank; read lamp means directed toward the light receptive members of said light responsive conduCtion means; read lamp power supply means; read lamp control means interposed in series with said read lamp means in a circuit across said read lamp power supply means to selectively complete a power circuit to said read lamp means; light controlling means physically interposed between said light responsive conduction means and said read lamp means to selectively pass a light pattern therethrough into preselected light receptive members in a pattern geometrically corresponding to the desired lighting pattern of the lamp units in the lamp bank; lamp unit power supply means to provide a pulsating lighting current for said lamp units; gate controlled rectifier means having independent cathode-anode circuits interposed in series with each lamp unit across said lamp unit power supply means; gate power supply means producing an intermittent gate signal having a peak voltage and current adequate to fire said gate controlled rectifier means; each light receptive element being interposed in a series circuit between the gate power supply means and each gate connection of said gate controlled rectifier means connected with the lamp unit corresponding thereto; a memory circuit power supply operable, when activated, to produce a filtered holding current at the output thereof; and memory circuit control means to selectively actuate said memory circuit power supply, the output of said memory circuit power supply being applied to a cathode-anode connection common to said gate controlled rectifier means.
 7. An apparatus as defined in claim 6 wherein said light controlling means comprises: an axial drum having longitudinal message cards mounted thereon; each of said message cards being provided with preselected apertures to pass light to selected light receptive members of said light responsive conduction means; and said light receptive members being longitudinally aligned adjacent to said drum in a position facing one of said message cards.
 8. An apparatus as defined in claim 7 wherein said read lamp means is mounted in a stationary position inside said drum and light therefrom is directed toward the light receptive members through one of said cards.
 9. An apparatus as defined in claim 7 further comprising: an intermittently operable motor mechanically connected to said drum to selectively shift said drum to bring a preselected card mounted thereon into a position interposed between said read lamp means and said light receptive members.
 10. An apparatus as defined in claim 6 wherein said light controlling means comprises: a plurality of cards each being apertured to provide a preselected light pattern therethrough from said read lamp means to said light receptive members; and indexing means operatively connected to said light controlling means to position a selected one of said cards between said read lamp means and said light receptive members. 